9/30/14 - (from a CARMA contributor) - The source of the frequently reported interference on AAR Channel 73 (161.205 MHz) has been located. It is the Norfolk Southern Railroad transmitting from a 180 foot tower with 280 watts ERP located at Columbus Avenue and Maplewood Avenue in Chicago. It is used by the NS Police, the channel is NXDN and it is encrypted. I can hear the channel as far west as Oswego and north in Buffalo Grove and beyond.